The WordPress team is actually working on creating a calmer, less-distracted editing experience for users in the next release. In the meantime, you create an undistracted editing experience using the Whitescreen plugin.
Compare the post editor before and after the plugin is installed:
With Whitescreen installed:
Much calmer and cleaner, isn’t it? If you want a minimal, clutter-free editing experience, this plugin will help you to focus on your content. Whitescreen is available for download for free from the WordPress repository.